The 5'-amino-2',4'-BNA, bearing a locked N-type sugar conformation and a P3'-->N5' phosphoramidate linkage, was found to be rapidly cleaved by acid-mediated hydrolysis when they formed a triplex with the target dsDNA. The fluorophore and quencher moieties were introduced into the 5'-amino-2',4'-BNA-modified oligonucleotide which was used as a novel and innovative DNA detection probe.